Direct Conversion of Biomass to Biodiesel Fuel

ABSTRACT

Disclosed is the direct conversion process for producing biodiesel from a biomass. The direct conversion process for producing biodiesel from a biomass comprises reacting a feed stock comprising a biomass and an alkylation reagent in a substantially oxygen free environment at a temperature sufficient to hydrolyze one or more lipid glycerides in the biomass and alkylated one or more fatty acids in the reaction. The process may comprise reacting a feed stock comprising an algal biomass and tetramethylammonium hydroxide in a substantially oxygen free environment at a temperature between 250° C. and 500° C. The direct conversion process for producing biodiesel may further comprise reacting oil containing lipid glycerides with an alkylation reagent at a sufficient temperature to esterify the oil. The fatty acid alkyl esters produced from the reacted feed stock are recovered. The recovered fatty acid alkyl esters, as an essential component of biodiesel, may be formulated into biodiesel.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Provisional Patent Application Ser.No. 61/015,926 filed on Dec. 21, 2007 and incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates in general to a process of producingbiodiesel directly from a biomass. In particular, the invention relatesto a process of producing fatty acid alkyl esters directly from abiomass using an alkylation reagent.

BACKGROUND

The recent emphasis on finding alternative energy sources to fuel theenergy needs of the United States and the world is leading to anaccelerated search for new fuels or new sources of fuel. Producing aliquid fuel from biomass, or biofuel, is an important focus of manyalternative energy strategies. Ethanol production from plant biomass isone example of this. Another example of a newer fuel is biodiesel.Refined vegetable oils have been the typical starting materials for theproduction of biodiesel. Biodiesel can be produced from the oils of manyplants. Biodiesel is an alternative, non-toxic, biodegradable andrenewable diesel fuel. These characteristics of biodiesel reduce theemission of carbon monoxide, hydrocarbons, and particulate matter in theexhaust gas compared to diesel fuel.

Biodiesel is commonly referred to as fatty acid methyl esters (FAMEs)which are usually obtained from oils extracted from soybean, sunflower,rapeseed or even waste cooking oil. Biodiesel production relies on achemical reaction called transesterification that transforms esters suchas triglycerides into mono alkyl esters. Conventionally, this reactionrequires a large excess of methanol, or in some cases ethanol, and anacid or a base catalyst under heated conditions.

In practice, the commercial production of biodiesel from plantfeedstocks involves a multi-step process that is time-consuming and notnecessarily economically attractive. Triglycerides in oils have beenesterified in a multi-step process using acidic or alkaline catalysts.The amount and type of catalyst necessary has varied widely dependingupon free triglyceride content of the oil. Initially, the oil feedstockmust be extracted. The oil extraction step is typically done in avariety of ways. Oil from plant material may be extracted by lysing andseparating, crushing, and centrifuging. The oil may be expressed withrollers, then separating the oil and discarding the residual organicmaterial. Oil can be extracted using chemicals. Benzene, ether andhexane have been used, with the downside to using such solvents beingthe dangers involved in working with the chemicals. Enzymatic extractionand osmotic shock are other methods that may be used. The oil is blendedwith an alcohol such as methanol, an acidic or alkaline catalyst isadded, and the blend is then heated and cooled. In thetransesterification, an acidic or alkaline catalyst is added to the oilwith anhydrous methanol to carry out the reaction. This multi-stepprocess is required because a feedstock having a free fatty acidconcentration, when exposed to an alkaline catalyst, produces a highconcentration of soap. Additional steps are typically required to removethe catalyst residue and strip off the lower alcohols.

SUMMARY OF THE INVENTION

Disclosed herein are direct conversion processes for producing fattyacid alkyl esters from a biomass. The recovered fatty acid alkyl estersas an essential component of biodiesel can be formulated into biodiesel.Therefore, the processes of the invention are useful for producingbiodiesel from a biomass.

A first embodiment of the direct conversion process for producingbiodiesel from a biomass comprises reacting a feed stock comprising abiomass and a alkylation reagent in a substantially oxygen freeenvironment at a temperature sufficient to hydrolyze one or more lipidglycerides in the biomass and alkylated one or more fatty acids in thereaction. The fatty acid alkyl esters produced from the reacted feedstock are recovered.

A second embodiment of the direct conversion process for producingbiodiesel from a biomass comprises reacting a feed stock comprising analgal biomass and tetramethylammonium hydroxide in a substantiallyoxygen free environment at a temperature between about 250° C. and about500° C. The reaction comprises hydrolyzing one or more lipid glyceridesin the algal biomass and methylating one or more fatty acids as they areproduced in the reaction. The fatty acid methyl esters produced from thereacted feed stock are recovered.

A third embodiment of the direct conversion process for producingbiodiesel comprises reacting oil containing lipid glycerides with analkylation reagent at a sufficient temperature to esterify the oil. Thereaction occurs in a substantially oxygen free environment. The fattyacid alkyl esters are recovered from the esterified oil.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views, and wherein:

FIG. 1 is a schematic diagram of an embodiment of the conversionprocess;

FIGS. 2A and 2B show the fatty acid methyl ester yield. FIG. 2A showsthe yield compared to temperature, and FIG. 2B shows the yield comparedto amount of tetramethylammonium hydroxide; and

FIGS. 3A and 3B show GCTOF-MS ion chromatograms of biodiesel from analgal sample and biodiesel from soybean oil, respectively.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Disclosed herein is a process for directly converting biomasses of algaeand other plant feedstocks to biodiesel fuel. The one-step processinvolves thermochemolysis with a single alkylation reagent at asufficient temperature under substantially oxygen-free conditions and atambient pressures. Also disclosed is a process for conversion ofglycerides to biodiesel with a single alkylation reagent at slightlyelevated temperatures under substantially oxygen-free conditions and atambient pressure.

As used herein, “biodiesel fuel” refers to any fuel, fuel additive,aromatic and aliphatic compound derived from a biomass disclosed herein.As used herein, “reaction” is intended to cover single step andmulti-step reactions which can be direct reactions of reactants toproducts or may include one or more intermediate species which can beeither stable or transient.

An embodiment of the direct conversion of biomass to biodiesel fuel isdepicted in FIG. 1. The reactor feed stock comprises a dried orpartially dried biomass 10 and an alkylation reagent 20. The feed stockcan be mixed and loaded into a reactor 30. The reactor 30 hastemperature control (not shown) to maintain the reactor 30 at a desiredtemperature. Inert gas 40 flows through the reactor to maintain asubstantially oxygen free environment. At the desired temperature,transesterification occurs. The lipid triglycerides of the dried orpartially dried biomass 10 are hydrolyzed and the fatty acids arealkylated, directly producing fatty acid alkyl esters (FAAEs), theessential biodiesel component. The following is the general reactionequation:

Glycerides+Alkylation Reagent=FAAEs+other products

The volatile FAAEs produced in the reaction are recovered. In thisembodiment, recovery is shown via a condenser 50. The FAAEs arerecovered as biodiesel 60 by well-known methods such as condensation.Byproducts such as glycerol, water or other water soluble compounds areseparated by density in the reactor 70 or by either density orvolatility in the condenser 80.

The individual elements of the process will now be described in detail.

As used herein, “biomass” means material harvested from a plant orplants. Depending on the particular plant or plants, the harvestedmaterial is used directly as reactor feedstock or processed further bywell-known methods to convert it into reactor feedstock. For example,algae can be used directly, partially dried, completely dried, or driedand partially reconstituted in water. It is contemplated that alkylationefficiency is positively correlated to the surface areas of the biomassavailable to the chemical reactions taking place during the processesdisclosed herein. In this regard, algae can be directly used becausethey are single-celled and have very high available surface area. Higherlevel plants such as soybean pods may be chopped and/or crushed into afine powder, for example, prior to introduction into the processesdisclosed herein, in order to increase the available surface area. It isrecognized that for each type of plant processed, the processing can beoptimized for higher yields of fatty acid alkyl esters from theprocesses disclosed herein. It is also recognized that more than oneplant, or biomass from a plant, can be used as feedstock to the reactor.The biomasses can be mixed before introduction introduced individuallyinto the reactor to be reacted together. It is also contemplated thatone individual type of biomass can be the feedstock.

Methods for determining the content of one or more fatty acid alkylesters in a mixture are well known in the art and otherwise set forthherein. See, for example, the references U.S. Pat. Nos. 5,525,126;6,855,838; and 6,965,044 and U.S. Patent Application Publication Nos.2007/0048848 and 2003/0158074. Accordingly, the yield of one or morefatty acid alkyl esters resulting from the processes disclosed hereincan be readily determined, alone or in combination with one or morewell-known methods, such as those described in the cited references.

The biomass may comprise plants that have been conventionally studied inan effort to obtain biodiesel from the extracted oil. Non-limitingexamples of such plants are corn, sunflower, olive, soybeans, rapeseed,wheat, sugar beet, sugar cane, jatropha, palm, sorghum, cassava, hemp,algae and the like. Dried or partially dried biomasses of such plantscan be used in the embodiments herein. These plants contain the oilyglycerides necessary for the direct conversion. Such plants also includethose described in U.S. Pat. Nos. 5,525,126; 6,855,838; and 6,965,044and U.S. Patent Application Publication Nos. 2007/0048848; and2003/6158074.

In particular, algae are contemplated as a biomass feed stock.Microalgae, prevalent in both fresh and marine waters, are remarkableand efficient biological factories capable of producing substantiallymore lipids than most typical land plants. For example, Botryococcusbraunii, a strain of green microalgae, contains around 30-45% of oilcontent in their dried biomass. Algal culturing requires significantlyless land than other plant feed stocks, which can affect agriculturalproduction. Microalgae are capable of producing about thirty times theamount of oil per unit area of land, compared to terrestrial crops. Theper unit area yield of oil from algae is estimated to be from between5,000 to 20,000 gallons per acre, per year (4.6 to 18.4 l/m² per-year);this is 7 to 30 times greater than the next best crop, Chinese tallow(699 gallons). See An in-depth look at biofuels from algae, Jan. 19,2007,http://biopact.com/2007/01/in-depth-look-at-biofuels-from-algae.html andJohn Sheehan, Terri Dunahay, John Benemann, Paul Roessler “A look backat the U.S. Department of Energy's Aquatic Species Program: Biodieselfrom Algae,” Close-out Report, U.S. Dept. of Energy (July 1998). Due tothe high growth efficiency of microalgae, the microalgae can efficientlyrecycle the inorganic carbon released from the petroleum combustion. Forthese reasons, algae are an ideal source from which to producebiodiesel.

The biomass may be used wet, but it is recognized that drying increasesthe yield of FAAEs. Even though dried algae may be an ideal choice tofeed the reactor considering the ease of use and probable highelbiodiesel production, the drying procedure, takes time. The dryingprocedure may also require energy if freeze-drying is used. Lipids canalso be degraded if the algal matter is left exposed to air too long.

The dried or partially dried biomass 10 is fed to the reactor 30 bymeans well-known in the art. The biomass 10 may be conveyed, augered orsprayed, for example. The reactor 30 may be of any type known in the artthat can operate at the temperatures required. The configuration of thereactor 30 in FIG. 1 is not consequential and is only an example ofreaction chambers that may be utilized.

Transesterification occurs in the reactor 30. Transesterification is theprocess of exchanging the alkoxy group of an ester compound with anotheralkoxy group. The biomass contains glycerides that undergo hydrolysis inthe reactor during transesterification. The glycerides may be mono-, di-or triglycerides. The ester links are severed during hydrolysis,producing free fatty acids.

The transesterification process continues with the alkylation of thefreed fatty acids. Methylation in particular refers to the alkylationprocess used to describe the delivery of a CH₃ group. A non-limitingexample of an alkylation reagent 20 used in the embodiments disclosedherein is tetramethylammonium hydroxide (TMAH). Other non-limitingsuitable alkylation reagents include tetrabutylammonium hydroxide,trimethylphenylammonium hydroxide, tetramethylammonium hydroxide,(m-trifluoromethylphenyl)trimethylammonium hydroxide, mixtures thereofand the like.

TMAH is a quaternary ammonium salt that can transesterify the biomass inone step. It can hydrolyze triglycerides and methylate the fatty acidssimultaneously at the proper temperature, thus directly producing fattyacid methyl esters, or FAMEs, the essential biodiesel component. Theby-products may include glycerol, water, trimethylamine, methanol orother water soluble compounds that can be easily separated by density orvolatility. TMAH thermally decomposes to trimethyl amine plus methanolin the following equation:

(CH₃)₄NOH→(CH₃)₃N+CH₃OH

The trimethyl amine (TMA) by-product to which the TMAH is converted maybe recycled and converted back to TMAH. As an example, the TMA can bereacted with methyl chloride gas in water to produce tetramethylammoniumchloride (TMAC) as disclosed in U.S. Pat. No. 4,845,289. Methanol reactswith hydrochloric gas to produce methyl chloride and the methyl chloridereacts with TMA to produce TMAC. The TMAC can be passed through an anionexchange resin (OH form) to convert the TMAC to TMAH. Other byproductsmay also be recovered and recycled or used in downstream processes. Forexample, the glyceryl backbone of the glycerides can be methylated toproduce triglyme, a commercially usable product. Other byproducts mayalso be recovered and recycled or used in downstream processes.

FAAE yields are affected by the amount of alkylation reagent added tothe reactor. FIG. 2A depicts the FAME yield based on differing amount ofthe methylation reagent TMAH added to the reactor feed stock. Theresults indicate in FIG. 2A that 0.6 ml of the TMAH used, which as TMAHin 25% methanol, is equivalent to 0.12 g TMAH, yielded 5% FAME. Asindicated, greater or lesser quantities of TMAH produced lower yields.These yields were determined using one gram of dried algal biomass.

The transesterification takes place in a substantially oxygen freeenvironment. As used herein, “substantially oxygen free environment”means that the oxygen content of the gaseous environment of a reaction,such as the transesterification reaction in the processes disclosedherein, is reduced compared to the oxygen content of air. Thus,substantially oxygen free environment contemplates any amount of suchreduction, including reduction of the oxygen to non-detectable levels.In this regard, substantially oxygen free environment also contemplatesthat there may be residual oxygen remaining in the system. To achievethe substantially oxygen free environment, the reactor can be purgedwith an inert gas using well known means to reduce oxygen. Oxygen mayalso be reduced by preheating the reactor to the operating temperatures,thereby burning off the oxygen in the system. It is contemplated thatthe reduction in the oxygen is positively correlated to the amount ofdesired fatty acid alkyl ester yield. Thus, maximum reduction in theoxygen content results in higher yields of fatty acid alkyl ester. Theoptimal amount of the reduction of oxygen is determinable by monitoringthe fatty acid alkyd ester yield from the processes of the invention bythe methods described herein. In other words, the desired yield can becompared under any substantially oxygen free environment and compared tothe yield of transesterification under air. In one embodiment, theoxygen content of the gaseous environment of the transesterificationreaction is selected from less than: 20%, 19%, 18%, 17%, 16%, 15%, 14%,13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1% and undetectableamounts of the total. In another embodiment, the oxygen content isselected from less than 5%, 4%, 3%, 2%, 1% and undetectable amounts ofthe total. In another embodiment, the oxygen content is selected fromless than 2% of the total. In another embodiment, the oxygen content isessentially zero, meaning it is undetectable.

The transesterification takes place under ambient pressure conditions.This reduces the cost of the process and increases the simplicity of theprocess. However, it is contemplated that the pressure can be reduced toless than ambient, allowing for a further reduction in operatingtemperature. It is also contemplated that the pressure may be increasedto allow for a more efficient control of reactor conditions and productcollection. The optimal amount of the reduction in pressure and/ortemperature is determinable by monitoring the fatty acid alkyl esteryield from the processes of the invention by the methods describedherein.

The transesterification occurs at a temperature sufficient to hydrolyzeone or more lipid glycerides in the biomass and alkylate one or morefatty acids in the reaction. Referring now to FIG. 2B, the yield ofFAMEs produced from this process using an algal biomass as a feed stockis graphed against the temnperature at which the reaction was run. Theresults indicate that the yields of FAMEs produced at temperatures of250 and 350° C. were about the same, approximately 3.2%. The yield wasthe highest (4.43%) at 450° C., and the lowest at 550° C. The low yieldat 550° C. indicates that some of the FAMEs might be degraded at thehigher temperature. It should be noted that although 450° C. achievesthe optimum biodiesel yield in this particular process embodiment and atatmospheric conditions, lower temperatures may be used to providesuitable yields under different conditions, such as at pressures belowatmospheric. Further, economics and energy requirements may make a lowertemperature more favorable depending on the associated product yield. Itshould be noted that product yield, measured by methods discussedherein, may be optimized by varying at least one of temperature,pressure, and oxygen level. Therefore, in one embodiment, it iscontemplated that temperatures as low as 100° C. will produce thedesired yield when at least one of pressure and oxygen level isadjusted. In another embodiment, the temperature is selected from thefollowing ranges: 100° C. to 550° C.; 150° C. to 500° C.; 200° C. to450° C.; 250° C. to 400° C.; and 300° C. to 350° C.

A second embodiment of the process of direct conversion to biodieselfuel is described below. The second embodiment is similar to the firstembodiment. Therefore, descriptions of like steps and elements will notbe repeated.

The reactor feed stock of the second embodiment comprises a glyceridebased oil and an alkylation reagent. The feed stock is mixed and loadedinto a reactor. The reactor has temperature control (not shown) tomaintain the reactor at a desired temperature. Inert gas sweeps thereactor to maintain a substantially oxygen free environment. At thedesired temperature, transesterification occurs. The glycerides of thefeed stock oil are hydrolyzed and the fatty acids are alkylated,directly producing FAAEs.

The glyceride based oil may be of plants or plant biomasses that havebeen conventionally studied in an effort to obtain biodiesel.Non-limiting examples of such plants are corn, soybeans, sunflower,olive, rapeseed, wheat, sugar beet, sugar cane, jatropha, palm, sorghum,cassava, hemp, algae and the like. The oil is extracted from the plantsor biomasses by conventional means known to those skilled in the art.

During transesterification, the glycerides of the oil undergo hydrolysisin the reactor during transesterification. The glycerides may be mono-,di- or triglycerides. The ester links are severed during hydrolysis,producing free fatty acids.

The transesterification process continues with the alkylation of thefreed fatty acids. One alkylation reagent that can be used in theembodiments disclosed herein is tetramethylammonium hydroxide (TMAH).However, it is to be understood that the alkylation reagent is notlimited to TMAH and may be other suitable alkylation reagents, examplesof which include tetrabutylammonium hydroxide, trimethylphenylammoniumhydroxide, tetraethylammonium hydroxide,(m-trifluoro-methylphenyl)trimethylammonium hydroxide and the like.

TMAH hydrolyzes the glycerides and methylates the fatty acidssimultaneously at the proper temperature, following the same reactionequation disclosed in reference to the first embodiment. The by-productsmay include glycerol, water, trimethyl amine, methanol or other watersoluble compounds that can be easily separated by density or volatility.The trimethylamine by-product to which the TMAH is converted may berecycled and converted back to TMAH as described above. Other byproductsmay also be recovered and recycled or used in downstream processes.

The reaction of the second embodiment occurs in the substantially oxygenfree environment at ambient pressure and sufficient temperature, asdiscussed in reference to the first embodiment. The volatile FAMEs arerecovered with the same means discussed above.

EXAMPLES

Examples are presented below. The examples are intended only to furtherillustrate the embodiments disclosed herein and are not intended tolimit the scope of the invention as defined by the claims.

An algal biomass was collected from the effluent of a local wastewatertreatment facility. This algae sample, dominated by diatoms as detectedunder microscope, was collected from the surface of the water and airdried. Another algal sample was collected from a local lake usingultrafiltration. Briefly, 60 L of water from the lake was concentratedto about 60 mL using tangential flow filtration with a 0.2 μm membrane.The concentrated algae sample was freeze dried. This sample consistedmainly of Pennate diatoms and Cryptomonas sp, as observed under amicroscope.

To prepare the algae for the chemoreactor, 1-2 grams of dried algae wasmixed with 1 ml TMAH (25% in methanol). It should be noted that TMAH(25% in water) can also be used. Tests indicate the yield with TMAH inmethanol is higher than that with distilled water, suggesting that boththe TMAH and methanol are directly involved the alkylation process. Itis contemplated that with the use of water, a portion of the water ismethylated to form methanol.

TMAH and FAME standards were obtained from Sigma. The mixture wasevaporated to near dryness or dryness under nitrogen over a period of 2hours and was loaded into an appropriate heating furnace (reactor) thatmay be programmed or set for temperature control. The reactor used wasmanufactured by Thermo Electron, model Lindberg Blue M, PF55035A-1. Thetemperature was ramped from room temperature to 450° C. in 15 min. andthen was held for 30 min before cooling down to room temp. Nitrogenswept the reactor and condenser at ambient pressure at a flow rate of20ml/min. The volatile products including the biodiesel were condensedusing an ice-cold trap (condenser). The top layer of the condensed fluidin the trap can be taken directly as the biodiesel product.

After being filtered through glass wool, the biodiesel collected fromthe chemoreactor was injected into Gas chromatography coupled totime-of-flight mass spectrometry GC-TOF MS (LECO Pegasus III) using thesplitless mode. The analyses were carried out with an autosampler (CTCAnalytics) integrated to the GC system (Agilent Technologies, 6890N)fitted with a 30 m×0.25 mm i.d. capillary column (0.25 μcm film of 5%diphenyl-95% dimethyl polysiloxane). Helium gas was used as a carriergas, and the temperature was ramped from 50 to 300° C. at 15° C. min⁻¹following injection. The select mass ion m/z 74 was used to quantify theamount of FAME in the samples based on both internal and externalstandards; added (tetracosane) according to Frazier S. W., Nowack K. O.,Goins K. M., Cannon F. S., Kaplan L. A., and Hatcher P. G.,Characterization of organic matter from natural waters usingtetramethylammonium hydroxide thermochemolysis GC-MS, J. ANALYTICAL &APPLIED PYROLYSIS, 70(1), 99-128 (2003). Using the direct conversionprocess disclosed herein in the chemoreactor, FAME content from thealgal biomass sample is about 3% of biomass. This yield is comparablewith the conventional fatty acid analysis of microalgal samples,suggesting an excellent efficiency for biodiesel transformation. SeeMansoui M. P., Frampton D. M. F., Nichols P. D., Volkman J. K.,Blackburn S. I., Lipid and fatty acid yield of nice stationary-phasemicroalgae: Applications and unusual C24-C28 polyunsaturated fattyacids, J. OF APPLIED PHYCOLOGY, 17, 287-300 (2005).

A comparison was done of the biodiesel derived from the algal biomasswith biodiesels derived from other plants and supplied commercially. Thegas chromatography coupled to time-of-flight mass spectrometry (GC-TOFMS) was used to compare the chemical constituents in biodiesel productsfrom the algal biomass with two biodiesel standards availablecommercially from Houston Biodiesel. One of the biodiesel samples wasmade from palm oil (palmitic acid), and the second one was made fromsoybean and chicken oil. Both the palm oil and soybean oil biodieselswere produced using the conventional transesterification involvingsodium hydroxide and methanol. FIGS. 3A and 3B show the analytical ionchromatograms (AIC) of a biodiesel sample derived from algal biomass andthe biodiesel standard derived from soybean oil, respectively.

As seen in FIG. 3A, the biodiesel sample from the algal biomass wasdominated by FAMEs of C16:0 (saturated fatty acid with 16 carbons) andC16:1 (singly unsaturated fatty acid with 16 carbons), accounting for64% of the total FAMEs. The peak at 1045 s in the chromatogram is theinternal standard added for quantification purposes (tetraosane). FAMEC14:0 and C18:1 accounted for 33% of the total area, followed by a minorcomponent of C18:0 with 3%.

As seen in FIG. 3B, the biodiesel from soybean oil showed similarcomposition with the sample, mainly containing C16:0, C18:0 and C18:1.Interestingly, acetic acid butyl ester at 260 s was also detected in thesoybean biodiesel. The biodiesel derived from palm oil had a similarpattern as that from soybean oil (data not shown).

In additional experiments, tetraethylammonium hydroxide andtetrabutylammonium hydroxide (25% in methanol) were used as thealkylation reagent. These two reagents were tested under the sameconditions as those used with the TMAH, using dried algae from the samesource. These two reagents convert triglycerides to fatty acids ethylesters and fatty acid butyl esters, respectively. Similar to TMAH, thedominant products are the ethyl or butyl esters of C14:0, 16:0 and 18:0fatty acids. It should be noted, however, that the quality of ethyl orbutyl esters may not be as good as the FAMEs because they are lessvolatile, which may make the combustion in the engine more difficultthan FAMEs.

FAMEs yields were also tested with commercially available soybeans, cornoil, olive oil and sunflower oil. The soybeans were ground in a mortarand pestle, and 1 g of ground soybeans was loaded to the chemoreactorfor biodiesel conversion. To obtain FAMEs from vegetable oils, only asmall amount of vegetable oil is needed. A mini-reactor was usedconsisting of glass tubes as described by Chefetz B., Chen Y., Clapp C.E., Hatcher P. G., Characterization of organic matter in soils bythermochemolysis using tetramethylammonium hydroxide (TMAH), SOIL SCI.SOC'Y OF AMN. J., 64 (2), 583-589 (2000). The FAME yields from the algaesamples are similar (3-6%), whether the chemoreactor or the glass tubesare used, so the conversion of vegetable oil in the glass tubes isexpected to be equivalent to that expected in the chemoreactor. Briefly,2 μL of vegetable oil was mixed with 200 μL TMAH (25% in methanol).After the methanol was evaporated tinder N₂, the glass tube was sealedunder vacuum. The glass tube was put in a furnace at 250° C. for half anhour. The FAMEs in the tube were rinsed out with ethyl acetate for GC-MSanalysis.

The soybeans generated 2.2% FAMEs. This yield appeared to be lowconsidering the high lipid contents in soybeans, about 20%. It iscontemplated that the reason for the low yield is the use of the mortarand pestle, resulting in a coarse powder, effectively reducing thesurface area of ground soy beans available to react. The corn, olive andsunflower oil were each converted to FAMEs resulting in a higherefficiency, ranging from 88-140%. This higher efficiency is expectedbecause vegetable oil is miscible with TMAH in methanol. Therefore, theavailable surface area for the reaction is much higher, resulting inmuch higher conversion efficiency than that of the solids.

The overall similar mass spectrometry patterns between biodieselsavailable commercially and the biodiesel produced from the algal biomasssuggest that the direct conversion process employed in the subjectdisclosure yields a nearly identical biodiesel to those availablecommercially. The procedure is robust and does not require extensiveprocessing like that for the traditional process. It is a directtransesterification from solid to liquid biodiesel products, as well asliquid to liquid biodiesel products.

While the invention has been described in connection with certainembodiments, it is to be understood that the invention is not to belimited to the disclosed embodiments but, on the contrary, is intendedto cover various modifications and equivalent arrangements includedwithin the spirit and scope of the appended claims, which scope is to beaccorded the broadest interpretation so as to encompass all suchmodifications and equivalent structures as is permitted under the law.All numerical ranges cited herein are inclusive of all values containedtherein, and include both endpoints in a range.

1. A process for producing biodiesel comprising: reacting a feed stockcomprising a biomass and an alkylation reagent in a substantially oxygenfree environment at a pressure and temperature sufficient to hydrolyzeone or more lipid glycerides in the biomass and alkylated one or morefatty acids in the reaction; and recovering fatty acid alkyl esters fromthe reacted feed stock.
 2. The process of claim 1, wherein thealkylation reagent is tetramethylammonium hydroxide and the recoveredfatty acid alkyl esters are fatty acid methyl esters.
 3. The process ofclaim 2, wherein the temperature is between about 250° C. and about 500°C. and the pressure is atmospheric.
 4. The process of claim 1, whereinthe biomass is an algal biomass.
 5. The process of claim 4, wherein thealgal biomass is a microalgal biomass.
 6. The process of claim 5,wherein the microalgal biomass is dried or partially dried prior toreacting.
 7. The process of claim 6, wherein the alkylation reagent istetramethylammonium hydroxide.
 8. The process of claim 7, wherein thetemperature is between about 250° C. and about 500° C.
 9. The process ofclaim 7, wherein the temperature is between about 400° C. and about 450°C.
 10. The process of claim 1, wherein the fatty acid alkyl esters arerecovered by condensation.
 11. The process of claim 1, wherein the fattyacid alkyl esters are formulated into the biodiesel.
 12. The process ofclaim 1, wherein at least one by-product of the processed alkylationreagent is converted and recycled into the feed stock.
 13. The processof claim 2, wherein a trimethyl amine by-product of the processedtetramethylammonium hydroxide is converted and recycled into the feedstock.
 14. The process of claim 1, wherein the process is one of a batchprocess and a continuous process.
 15. The process of claim 7, whereinthe ratio in grams of microalgal biomass to tetramethylammoniumhydroxide is about 1:0.12.
 16. The process of claim 1, wherein thealkylation reagent is selected from one or more of tetramethylammoniumhydroxide, tetrabutylammonium hydroxide, trimethylphenylammoniumhydroxide, tetraethylammonium hydroxide, and(m-trifluoromethylphenyl)trimethylammonium hydroxide.
 17. The process ofclaim 1, wherein the substantially oxygen free environment comprisesless than or equal to two percent oxygen.
 18. The process of claim 1,wherein the pressure is less than atmospheric.
 19. The process of claim1, wherein the pressure is greater than atmospheric.
 20. A process forproducing biodiesel, the process comprising: reacting oil containinglipid glycerides with an alkylation reagent at a sufficient pressure andtemperature to esterify the oil, wherein the reaction occurs in asubstantially oxygen free environment; and recovering fatty acid alkylesters from the esterified oil.
 21. The process of claim 20, wherein thealkylation reagent is tetramethylammonium hydroxide and the temperatureis between about 250° C. and about 500° C.
 22. The process of claim 20,wherein the alkylation reagent is selected from one or more oftetramethylammonium hydroxide, tetrabutylammonium hydroxide,trimethylphenylammonium hydroxide, tetraethylammonium hydroxide and(m-trifluoromethylphenyl)trimethylammonium hydroxide.
 23. A process forproducing biodiesel from an algal biomass, the process comprising:reacting a feed stock comprising an algal biomass andtetramethylammonium hydroxide in a substantially oxygen free environmentat a temperature between about 250° C. and about 500° C., the reactioncomprising hydrolyzing one or more lipid glycerides in the algal biomassand methylating one or more fatty acids in the reaction; recoveringfatty acid methyl esters from the reacted feed stock; and formulatingthe fatty acid methyl esters into biodiesel.
 24. The process of claim23, wherein the algal biomass is dried or partially dried prior toreacting.
 25. The process of claim 23, wherein the fatty acid methylesters are recovered by condensation.
 26. The process of claim 23,wherein a trimethyl amine by-product from the processedtetramethylammonium hydroxide is converted and recycled into the feedstock.
 27. The process of claim 23, wherein the temperature is betweenabout 400° C. and about 500° C.
 28. The process of claim 23, wherein thesubstantially oxygen free environment comprises less than or equal totwo percent oxygen.